While Hurricane Sandy raged over the New York metropolitan area, the underground infrastructure of the city began to flood. Now Amtrak is revealing that they could have let Penn Station flood instead of the Hudson River tunnels, using a long-forgotten barrier designed to protect the city during World War II.

As the storm waters surged into the subterranean world beneath New York, city officials had to conduct a triage of sorts. Some assets would be able to survive the storm, and others would potentially be destroyed, and sometimes it was one or the other. In the case of the tunnels under the Hudson River that carry Amtrak trains into and out of the city, officials knew that they had a potential wildcard, according to WNYC:

In a conference call about disaster planning, Secretary of Housing and Urban Development Shaun Donovan described a meeting he had with transit executives where they discussed putting floodgates on transit tunnels.

"The executive from Amtrak said, well we had a barrier that could have closed off our Hudson River tunnel, but if we closed it, Penn Station would have flooded instead," Donovan summarized the Amtrak exec as saying.

A former employee told WNYC that the barrier was created to protect the transportation system from attack and other explosions during the Second World War, but it was apparently never used. The barrier worked by cutting off the mouth of the tunnel, but a lake would have been created right at the entrance to Penn Station and could have filled the entire thing.

It's hard to imagine the kind of calculus that would be running through someone's mind when trying to decide which part of vital infrastructure to swamp with seawater, though they probably made the right call. New York's Penn Station is a huge complex, serving as a hub not only for Amtrak, but also the nation's busiest commuter rail system with the Long Island Rail Road, New Jersey Transit, and the 1,2,3 and A,C, and E subway lines.

To try to rehabilitate all that would have been an enormous task, even bigger than the cleanup we currently face. As it stands, the Montague Tunnel, which carries the subway system's R train under the East River, was completely flooded, and now faces a 14-month long shutdown and repair. Cutting one subway line in half is one thing. Cutting Amtrak in half, at least in the Northeast, is another.